package com.can.lesson01.utils;

import java.io.IOException;
import java.io.InputStream;
import java.sql.*;
import java.util.Properties;

public class JdbcUtils {

    private static String driver = null;
    private static String url = null;
    private static String username = null;
    private static String password = null;

    static{
        try {
            //getClassLoader获得该类的装载器
            //getResourceAsStream用给定的名查找资源
            //当前是从 src路径开始
//            InputStream in = JdbcUtils.class.getResourceAsStream("/db.properties");//这种方式要加 '/'
            InputStream in = JdbcUtils.class.getClassLoader().getResourceAsStream("db.properties");
            Properties properties = new Properties();
            properties.load(in);
            driver = properties.getProperty("driver");
            url = properties.getProperty("url");
            username = properties.getProperty("username");
            password = properties.getProperty("password");

            //1.驱动只加载一次
            Class.forName(driver);

        } catch (IOException | ClassNotFoundException e) {
            e.printStackTrace();
        }
    }

    //获取连接
    public static Connection getConnection() throws SQLException {
        return DriverManager.getConnection(url,username,password);
    }

    //释放资源
    public static void release(Connection conn, Statement st, ResultSet rs){
        if (conn!=null){
            try {
                rs.close();
            } catch (SQLException e) {
                e.printStackTrace();
            }
        }
        if (rs!=null){
            try {
                rs.close();
            } catch (SQLException e) {
                e.printStackTrace();
            }
        }
        if (st!=null){
            try {
                rs.close();
            } catch (SQLException e) {
                e.printStackTrace();
            }
        }
    }
}
